Dishwashers are frequently also referred to as “warewashers”, since they can be used not only to clean dishes and cutlery, but, for example, also to clean pots, pans, trays and similar items. Dishwashers or warewashers may be programmable machines of the box-type. These can be rack push-through machines (hood-type warewashers), or front loaders, particularly under-counter machines.
From EP 0 808 894 B1, a washware cleaning method is known, containing the steps: preliminary cleaning by spraying the washware with a pre-cleaning solution, main cleaning and after-rinse. To the pre-cleaning solution are added at least one alkali component and at least one complexing agent. The document does not state whether the method relates to a programmable machine (box-type warewasher) or a conveyor warewasher.
Commercial dishwashers or utensil washers (commercial warewashers) normally operate in two main process steps, namely first washing with washing liquid and then rinsing clear with heated fresh water, to which rinse aid is added. The washing liquid contains water and added detergent.
In order to be able to perform these two process steps, a commercial dishwasher is normally equipped with two mutually independent liquid systems, which are completely separate from one another. One of these two liquid systems is a washing liquid circuit, which is responsible for washing the washware and is realized with previously used liquid from a wash tank. The other liquid system is a clear-rinsing liquid system, which has a water heater (boiler) for heating fresh water.
The main object of the clear-rinse with clear-rinsing liquid is to remove suds present on the washware. In addition, the clear-rinsing liquid which flows off into the wash tank in the course of the clear-rinse serves to regenerate the washing liquid in the wash tank.
Before new fresh water is supplied for the clear-rinse, the same quantity of washing liquid is pumped off from the wash tank into the on-site waste water system.
One particular type of commercial dishwashers in the form of programmable machines are hood-type dishwashers. Their treatment chamber for the cleaning of washware is surrounded by a hood. The hood can be lifted upwards for the loading of the treatment chamber and can then be lowered again for the treatment of the washware. Hood-type dishwashers are almost always provided with a feed table and a delivery table. The feed table is in many cases configured as a pre-cleaning station for the preliminary cleaning of the washware by rinsing and/or by manual removal of dirt deposits from the washware before this is pushed into the hood-type dishwasher in a washware rack. The preliminary cleaning by pre-rinsing is normally done manually. The pre-rinsing in the course of the preliminary cleaning is generally performed with on-site cold or pre-heated fresh water. In some cases, an additional cleaning chemistry is further used for the pre-rinsing. The delivery table serves for the drying and unloading of the washware racks.
Studies led within the framework of the invention revealed that, for the preliminary cleaning of the washware, depending on the type of washware and its dirt contamination level, about 2 to 3 liters of fresh water are used.
It would be desirable to provide a facility by which the efficiency of the dishwasher can be improved.